The present invention relates to an apparatus for the isostatic measurement of the permeability of a material to the passage therethrough of a gas or vapor.
More particularly, the present invention is directed to such a process and apparatus which is capable of determining the permeability of a material in sheet or foil form, as well as material in the form of an enclosed or three-dimensional wrapper or container.
U.S. Pat. Nos. 3,301,043 and 3,352,146 disclose systems for measuring the permeability of materials by a manometric process wherein a pressure difference is created between opposite sides of the material. Such systems have the advantage that measurable results are obtained relatively rapidly.
However, while these prior art systems relatively accurately duplicate certain situations, such as wherein bottle or can-type containers contain therein a product, such as beer, maintained under pressure, these systems obviously fail to duplicate actual conditions existing in a great many other types of packaging situations. For example, a great many types of products are wrapped or enclosed within a wrapping material wherein the pressure within the wrapper is the same as the pressure (normally atmospheric) surrounding the wrapper. It will be apparent that the above noted prior art systems, wherein a pressure difference is created across the material, do not test for permeability or leakage of the material under conditions corresponding to actual use of the material.